Sales of mechanical exoskeletons cap decades of scientific tinkering that included a 1,500-pound General Electric clunker in the 1960s. Strapped to users' bodies and powered by lithium-ion batteries, the emerging technology has led to some models that sell for about $70,000, weigh less than 50 pounds and are nimble enough to let wearers dance the Macarena.

"We're now seeing a golden age in which we can produce this technology and derive benefit from it," said Keith Maxwell, the business development manager for Lockheed's program. "There's a host of industries where this works."

The first commercial sale of a medical unit - not for lab or hospital tests - came in September, pioneering a field that may produce $400 million in annual revenue by 2020, according to technology consultant ABI Research. Lockheed says it hasn't estimated the value of any contracts for its under-development military version, known by the acronym HULC, or for the nascent industrial market its Mantis device will enter this year.

Military boost

The machines may follow a classic arc from Pentagon research project to fixture on an assembly line, similar to the development of lasers, said Paul Saffo, managing director of foresight at investment advisory firm Discern in San Francisco.

"The medical devices get the most attention, the military funds it and the first mass application is industrial," Saffo said.

Developing technology for both civilian and military use would be a boost for Lockheed, the world's largest defense contractor, as it confronts reductions in U.S. arms spending. Parker Hannifin, the biggest manufacturer of motion and control devices, is seeking to expand into the medical industry.

Commercial exoskeletons are just echoes of Hollywood's take on Iron Man's bulletproof garb and the armor that Heinlein envisioned for his futuristic warriors.

Ekso Bionics' device for spinal patients looks like the lower half of a black metal skeleton able to stand by itself on foot pads. Parker Hannifin's medical model breaks into five pieces and resembles elongated plastic football thigh pads worn on the sides of users' legs.

Motors, sensors

Electric motors amplify the strength in their wearers' limbs or, in the case of those in wheelchairs, supply power. Computers and sensors help provide balance and guidance.

Argo Medical Technologies Inc. entered the market last year, with an exoskeleton to assist patients who have lost the use of their legs. Parker Hannifin's Indego model is also designed for those users, and will go on sale in 2014 at a price the company says is competitive with Argo's $67,230 unit.

In between those introductions will come Lockheed's Mantis, which the company envisions as finding a home in any industry in which workers must hold heavy equipment that can cause fatigue and back injuries.

While Ekso Bionics' Harding sees exoskeletons on an evolutionary path toward ever-greater sophistication - much as brick-like handsets in the early 1990s morphed into today's smartphones - it may not be that easy to cut costs, simplify the technology and ensure widespread adoption.

"Even though there are processors and sensors, there's still a lot of physical matter that has to be machined and built," said Discern's Saffo, who is also a consulting associate professor at Stanford University's engineering school.

Vast potential

The other limitation is battery life. Batteries can be made only so powerful before turning into a bomb, Saffo said. Boeing Co. knows the risks in working with larger versions of the lithium-ion cells found in mobile phones and other electronic gadgets: It's still trying to figure out the cause of electrical faults that grounded its 787 Dreamliner.

"Until you have higher-density power storage, you're always going to be looking for a plug for your exoskeleton," Saffo said.

The exoskeleton industry is attractive because the potential is vast and the large competitors are few, according to Lockheed and Cleveland's Parker Hannifin.

Back strain is the most common non-combat injury because of the heavy packs soldiers carry, Maxwell said. Lockheed licensed some technology from Ekso Bionics to produce the HULC, which is set to enter a second development phase this year as the system is refined so it can be worn under a uniform.